1. Field of the Invention
The invention described herein relates to a photographic film unit comprising a photographic film disk attached to a central hub and adapted to cooperate with other photographic apparatus. The film unit may be incorporated in a compact cartridge assembly for cooperation with an associated camera.
2. Description Relative to the Prior Art
It has become commonplace in recent years to package photographic film in a cartridge, cassette, magazine or the like designed to afford convenient loading of a camera by simple insertion of the film-loaded package into the camera. A typical such package may be configured to accommodate an elongated strip of photosensitive roll film that is advanced lengthwise to bring successive spaced exposure areas into optical alignment with the camera's lens structure for exposure to scene light. Alternatively, it is also well known to position a plurality of exposure areas in a generally circular array on a disk-shaped sheet of film and to rotate such sheet incrementally to bring successive exposure areas into position for exposure by the camera. Typical advantages of such a film disk over roll film include the relative compactness of the film package and the relative flatness exhibited by the film.
An illustrative example of a film disk having circularly-arranged exposure areas is shown in U.S. Pat. Nos. 509,841 and 517,539 which issued respectively, on Nov. 28, 1893 and Apr. 3, 1894. As seen therein, a plurality of imaging areas are located along the outer perimeter of a film disk. The disk is received within a camera (sold under the trademark "Photoret") and is clamped, along its outer perimeter, to a flat internal face of the camera back wall. Incremental rotation of the back wall with respect to a lens and shutter assembly carried by the camera front wall moves successive exposure areas into optical alignment with the camera lens. Although the camera includes means for precluding the same exposure area from being exposed twice in immediate succession, no provision is made for preventing the film disk from being double exposed by rotation through more than one complete revolution. The positioning of the exposure areas on the film is determined solely, and thus relatively imprecisely, by camera mechanisms regulating the relative rotational movement of the camera back wall.
U.S. Pat. No. 1,773,106 which issued on Aug. 19, 1930 describes a film disk and an associated camera wherein the disk is mounted to the camera by means of a central hole in the disk which receives the threaded end of an incrementally-rotatable camera shaft. The disk is secured to the shaft by a threaded fastener, whereby rotation of the shaft brings successive exposure areas into position. In addition to including means for preventing a given exposure area from being immediately re-exposed, the described camera also includes an interlock device controlled by the film compartment door to prevent operation of the camera shutter after the disk has made one complete revolution and until the door is opened to remove the exposed disk. However, no means is provided to prevent an exposed film disk from being re-inserted into the camera and re-exposed therein, and the exposure areas are positioned on the disk solely by means of camera mechanism limiting the arc of travel of the rotatable camera shaft.
An additional disadvantage associated with each of the camera-film arrangements described above is the absence of a protective encasement for containing the film disk. As a consequence, loading the film into the camera may prove to be at least inconvenient, inasmuch as loading must be done in total darkness, and may lead to mis-loading or to damage to the film. U.S. Pat. No. 2,446,200 issued on Aug. 3, 1948 and U.S. Pat. No. 2,531,651, No. 2,531,652 and No. 2,531,653 all of which issued on Nov. 28, 1950 describe a product which was sold under the trademark "Foto-Disc" wherein a film disk is clamped between two plates in a protective cartridge to which a lens and shutter assembly may be temporarily attached. A movable shield covers an exposure window in the cartridge during such times as the camera is detached from the cartridge. The user rotates a ring carried by the cartridge to advance the film disk into position relative to the attached camera preparatory to exposure. An abutment on the cartridge precludes rotating the film disc through more than one complete revolution, while cartridge detents establish indexing for the respective exposure areas.
Another camera-cartridge combination produced in Japan beginning in about 1949 and marketed under the trademark "Petal" comprised a sub-minature camera and an all-metal disk film cartridge. The cup shaped rear casing of the cartridge, to which the perimeter of the film disk is clamped, is received within and keyed to a rotatable externally accessible portion of the camera housing. The front cartridge wall includes an aperture covered by a pivotal spring-loaded shield. Initial rotation of the cartridge uncovers the aperture and subsequent incremental rotation, indexed by a detent device, brings successive exposure areas into optical alignment with the camera lens. No means are provided for preventing double exposures and the cartridge apparently must be returned to the film processor for reloading.
Still another sub-minature camera of this same general type was sold under the trademark "Steinneck" and is disclosed in U.S. Pat. No. 2,625,087 issued on Jan. 13, 1953. This camera resembles a wrist watch and uses a film cartridge intended to be reloaded by the film processor. The cartridge includes two superimposed closure plates, each of which is provided with an exposure window and an arcuate transport tooth window. One of the closure plates is stationary with respect to the cartridge housing and the other one is rotatably moveable. Whenever the cartridge is removed from the camera, the windows in these two plates are out of alignment with each other to prevent accidental exposure of the film. Upon installation of the cartridge into the camera relative rotation of the movable plate aligns the exposure windows with the camera's objective lens and shutter and also aligns the arcuate windows to admit a film transport tooth into the interior of the cartridge. A rotatably supported hollow bushing within the cartridge carries a transport disk that is located immediately behind the closure plates and provided with spaced exposure apertures and with corresponding peripheral transport notches. Stacked on the bushing behind the transport disk are the film disk, a film positioning disk, a tension disk and a counter disk, each of which is provided with an edge notch engaged with a pin on the transport disk to keep all of these disks in fixed rotational relation to each other. Each operation of the shutter operating lever causes the shutter momentarily to open and reclose and then actuates the movement of the transport finger, which engages the next transport notch in the transport disk and rotates the latter to thereby angularly move all of the magazine disks in unison so that the next exposure area is brought into exposure position. The counter disk is provided with a circular row of numbers corresponding to the film exposures and a window in the back of the magazine allows the photographer to see the counter disk number indicative of the number of exposures remaining to be made. Removal of the magazine from the camera automatically closes the exposure and transport finger windows and, if not all of the available exposures have been used, the magazine can later be reinstalled to expose the remaining exposure areas. The same transport disk pin that prevents relative rotation between the various disks also cooperates with a stationary plate behind the counter disk to limit the rotation of the rotatable disks to 360 degrees, thereby preventing reexposure of the film in a previously exposed cartridge.